Restorative dentistry, which entails the treatment of primary caries and replacement of defective and failed restorations, constitutes a major percentage of all dental treatment. The recent influx of new dental materials for preventive and restorative therapy and an increased emphasis on esthetics versus longevity or economy have confounded the development of standardized treatment plans. Furthermore, methods for assessment of the "quality" of restorations under in vitro conditions are not available to a clinician who must base his or her judgment of acceptability or unacceptability on relatively imprecise instruments and procedures. Thus, it is not surprising that there is a wide variability in clinical judgment on whether to retain or replace dental restorations of questionable quality. The objective of this symposium is to assess existing research data and attempt to standardize clinical decisions with respect to preventive therapy, restorative treatment, and the management of defective restorations. Presentations will focus on the assessment of restoration quality, prognosis of specific restoration-tooth-patient conditions, causes of restoration failure, and treatment plan options. The trend towards a preventive rather than a restorative philosophy will also be addressed. The specific aims of the symposium are to: 1) establish guidelines for assessment of restoration quality, 2) summarize the failure frequency and life expectancy of sealants, amalgams, composites, and crown and bridge restorations, 3) standardize criteria for preventive or restorative treatment based on a classification of patient risk, 4) determine the optimum course of diagnosis and treatment for patients with suspected contact allergies to restorative materials, 5) assess the current philosophy of restorative dentistry, 6) examine the variability of the decision- making process in the development of treatment plans, 7) establish criteria for clinical selection of dental materials based on properties, technique sensitivity, and clinical performance data, 8) assess the influence of bacterial leakage around dental restorations, 9) characterize existing methods for detection of caries and assessment of the progression of primary caries and carious lesions associated with dental restorations, and 10) identify areas for future research.